Timing belt problems typically come without warning. There is no screech that lets you know it's time to replace it. If your car drives regularly, but the engine suddenly stops making a thud and you just can't get it started again, then the timing belt is likely to blame. The transmission on the engine must be perfectly calibrated, otherwise the valves and pistons will collide resulting in very expensive repairs. If the belt has snapped, then you need to check the valves for damage before replacing the belt. A technical manual for your car will help you figure out if the timing belt has damaged the valves or not.
Steps
Part 1 of 4: Buying the Belt
Step 1. Before disassembling the old belt, buy a new one
If you are doing normal maintenance, you need to get the new replacement part. If the belt is broken or has come off, then you have to wait to remove the old one before buying a new one, so you can compare products and be sure you are getting the right model for your car.
Most cars are fitted with rubber timing belts, while steel ones were more common in the past. These spare parts are available in most auto parts stores for a few euros and you should have them replaced every 140,000-190,000km, depending on the engine type
Step 2. Collect all information about your vehicle
You need to know the manufacturer, model and year of production, as well as the type and size of the engine. Some models have undergone variations during the same year of production, so the VIN number may prove useful. You can purchase the timing belt at your dealer or auto parts store.
Step 3. Remember to buy the gaskets and their adhesive which are indispensable for the assembly
The shop assistant will be able to tell you what you will need. There are timing belt replacement kits that contain everything you need, including gaskets, to get the job done.
Part 2 of 4: Expose the Strap
Step 1. Disconnect the negative battery cable
Check that you have the car radio security code (if applicable) and make a note of the various radio stations you selected so that you can quickly reset them at the end of the job.
Step 2. Remove the alternator belt.
Depending on the engine model, it may be necessary to remove the serpentine belt to reach the timing belt. Loosen the nuts, push the alternator to create some slack in the belt and take it apart.
Step 3. Remove all accessories that prevent access to the timing belt cover
For example, you could disassemble the power steering pump, alternator and air conditioning compressor. Do not remove the pressurized fittings of the compressor, most of the compressors can be unscrewed and disassembled without having to drain the fluid from the system. Remove the rocker cover to access the timing belt.
Step 4. Remove the distributor cap, if it is present on your vehicle
You will need to pry the closing hooks to disassemble the cap and remove the screws that secure it.
Some modern cars with electronic ignition do not have a distributor. These are equipped with a crankshaft and camshaft position sensor. The most important thing is to determine the top dead center (TDC) of the first cylinder; for this you must consult the technical manual of the car, since it is a reference that changes according to the car model
Step 5. Align the timing references
Use a wrench or socket to turn the crankshaft nut until the mark on the crankshaft pulley aligns with the 0 ° mark on the timing scale.
- Check that the distributor rotor is aligned with the reference mark on the distributor housing indicating that the rotor is in the right position to ignite combustion in the first cylinder. If this alignment does not occur, rotate the motor one more full revolution.
- Do not proceed with this operation on an interfering engine unless you are certain that the timing belt is intact. If the valves weren't bent at the time of the belt breaking, they could do it while cranking the engine manually without a specific tool.
Step 6. Evaluate if you need to remove the harmonic balance pulley to be able to disassemble the timing belt
The cover is sometimes "straddled" over the end of the crankshaft and this pulley does not allow you to remove the cover without first removing it. Remember that in this case you will need a new gasket to reassemble the pulley, and you will also need to get special tools to disassemble the pulley and gears respecting the alignment.
Step 7. Remove the bolts or screws securing the timing belt cover
Remove this cover from the engine compartment. Some engines are equipped with a two-piece crankcase. Remove any components or accessory drive belts that may interfere with subsequent operations. This stage of the work varies according to the vehicle model; always refer to the technical manual to understand which pieces you need to disassemble.
Step 8. Verify proper alignment between the crankshaft and camshaft and the timing marks
Many engines have a reference point or line on the pulleys and / or sprockets and these marks should align with those found on the engine block, cylinder head or shaft of accessory engines. On some engines, the reference line on the crankshaft pinion aligns with the parting line of the first camshaft support tower.
This step is critical if you are replacing a broken timing belt. Read the technical manual to know the right alignment procedure for your vehicle and correct any errors before installing the new belt. These marks are sometimes also shown on a label above the belt cover itself
Step 9. Look around the belt for any oil leaks
Also look close to the crankshaft and its gaskets and don't forget the valve cover and oil pan. Inspect the water pump and its pipes to make sure there are no coolant leaks. These problems can be fixed quickly before installing the new belt.
Part 3 of 4: Loosen the Belt
Step 1. Loosen the fixing nuts securing the belt tensioner using a special tool, following the instructions in the technical manual
Do not completely disassemble the belt tensioner, unless you need to replace it. Instead, rotate the spring tensioner away from the belt and then re-tighten the retaining nuts to keep it in a loose position.
Step 2. Check the idler pulley for damage, dents or cracks
Spin it and pay attention to clicking or creaking noises that indicate the absence or wear of some bearings. Uneven wear on the back of the old timing belt indicates misalignment between the tensioner pulley and the belt itself due to bad ball bearings.
If you find any signs of damage or wear on the ball bearings, replace the belt tensioner pulley. Bearings must be constantly lubricated and over time they dry, wear, loosen, break or get stuck; so it is worth changing them, if they are not new
Part 4 of 4: Mount the Belt
Step 1. Remove the belt from the sprockets
Now that it is not energized, you should be able to easily remove it from the sprockets. An old timing belt may stick to the pulley notches and you will need to gently pry it up with a screwdriver to detach it. Check the belt pulleys and water pump to be sure some replacement is not required before fitting the new belt.
Step 2. Replace the belt and start reassembling the pieces
Tighten it according to the torque specifications indicated in the engine manual, paying particular attention to the nut fixing the crankshaft pulley which, in general, must be tightened to very high values.
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If your car is equipped with a hydraulic belt tensioner, it may be necessary to push the piston back into the cylinder once the pawl is released. Put it in a vise and squeeze it until the holes line up and allow you to insert a locking pin. When the pin is in place, then you can reassemble the belt tensioner; later, once the timing belt has been mounted, you can remove the pin to allow the belt tensioner to tension the belt.
Change a Timing Belt Step 16
Advice
- A beginner should purchase a (rather expensive) manual with the technical specifications of the car model and engine to which the timing belt needs to be changed. These manuals are intended for experienced mechanics and require knowledge on the subject; they are very detailed and show the belt tension values, the tightening torque of the bolts, the points where the screws are placed and so on.
- It is important to always follow the specific instructions for the car model and year of construction, especially if you are not an expert. The technical manual, while expensive, will pay for itself with just a repair you managed to do yourself.
- For some vehicles a special tool is required to reach the tensioner fixing bolts which are hidden by the engine mount, while in other cases you will need different tools to disassemble the spring tensioner. Most engines have a spring-loaded belt tensioner that can be operated with standard socket or wrenches, while some models require an Allen key.
- Timing belts are subject to wear. In most cases it should be replaced every 97,000-127,000 km as preventive maintenance. They can break causing extensive damage to the engines with interference, as the valves and pistons, now out of sync, collide. Regular replacement of this piece allows you to avoid very expensive repairs later; do not wait for the belt to break and damage the engine.
- The timing belt synchronizes the valves and pistons. When not properly calibrated, it causes contact between these elements, just like in the machine guns of WWII aircraft which, without a synchronization mechanism, would have fired directly at the propeller blades.
- If the timing belt is broken, you need to figure out if the engine valves are bent. In this case, major engine repairs are required. This is called an interference motor, meaning that the piston will make contact with the valve if the belt breaks. If, on the other hand, you are dealing with an interference-free engine, then the valves and pistons will not collide if the belt fails.
